Choosing Data and Behavior: Elevators, Employees, and Stacks

If a queue and a stack are both just a list inside, what actually makes them two different types?

Finger exercises

Short drills on what this video just taught. Write the code, run the checks, and reveal the answer only if you are stuck.

0 / 5 passed

Exercise 1 of 5

A list stored the other way

cells holds a list built the second way the video described — memory allocated here and there, wherever there was room. Each key is a memory address, and the value stored there is a two-item list: the element's value, and the address of the next element. The last cell's next address is None, and start holds the address of the first element.

Follow the chain from start and collect the values in list order into values, an ordinary Python list. The order the addresses happen to be written in cells is not the list's order.

(Hint: while, is not None, and the list method .append() are all useful here.)

# Exercise 1: recover the ordinary list hiding in this scattered layout.
cells = {
    412: [3, 118],
    877: [4, 412],
    118: [9, 654],
    301: [7, 877],
    654: [1, 205],
    205: [8, None],
}
start = 301

values = []

# your code here

# Exercise 1: recover the ordinary list hiding in this scattered layout.
cells = {
    412: [3, 118],
    877: [4, 412],
    118: [9, 654],
    301: [7, 877],
    654: [1, 205],
    205: [8, None],
}
start = 301

values = []

# your code here

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⌘/Ctrl + Enter runs

is a list holding one value per cell

follows the next-addresses instead of reading the cells top to bottom

recovers the values in list order

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